The Twenty-sixth Amendment to the United States Constitution established a nationally standardized minimum age of 18 for participation in state and local elections. It was proposed by Congress on March 23, 1971, and it was ratified by three-quarters of the states by July 1, 1971.

Birch Evans Bayh Jr. was an American Democratic Party politician who served as U.S. Senator from Indiana from 1963 to 1981. He was first elected to office in 1954, when he won election to the Indiana House of Representatives; in 1958, he was elected Speaker, the youngest person to hold that office in the state's history. In 1962, he ran for the U.S. Senate, narrowly defeating incumbent Republican Homer E. Capehart. Shortly after entering the Senate, he became Chairman of the Subcommittee on Constitutional Amendments, and in that role authored two constitutional amendments: the Twenty-fifth—which establishes procedures for an orderly transition of power in the case of the death, disability, or resignation of the President of the United States—and the Twenty-sixth, which lowered the voting age to 18 throughout the United States. He is the first person since James Madison and only non–Founding Father to have authored more than one constitutional amendment. Bayh also led unsuccessful efforts to ratify the Equal Rights Amendment and eliminate the Electoral College.